I think a photo is only useful if the person is using their photos in their posts. For instance if I post about my trip to Thailand, and the post is full of travel shots of me prancing around beaches, etc. It might be justified for a user to wonder if I'm the lady in the pictures or just someone who found these pictures on the internet.
This has been an issue in the past, which is why people are suspicious and lacking trust!
As I said, "we want to build a community of trust" meaning we aren't there yet!